A known approach for monitoring pellicle degradation involves visual inspection of the pellicle to detect cracks at its attachment to a photomask and/or unwanted material aggregation on the pellicle. However, a visual inspection can lack the precision required to generate reliable results and often occurs after the fact, preventing right-in-time repelling.
A need therefore exists for methodology and an apparatus enabling in-situ contactless pellicle degradation monitoring that is independent of visual inspection.